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Yamashita, Tsuyoshi. "Unraveling photonic bands : characterization of self-collimation in two-dimensional photonic crystals." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-06072005-104606/.
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Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2006.Summers, Christopher, Committee Chair ; Chang, Gee-Kung, Committee Member ; Carter, Brent, Committee Member ; Wang, Zhong Lin, Committee Member ; Meindl, James, Committee Member ; Li, Mo, Committee Member.
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Upham, Jeremy. "Dynamic Photon Control by Photonic Crystals." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142228.
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Chen, Vincent W. "Fabrication and chemical modifications of photonic crystals produced by multiphoton lithography." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45918.
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This thesis is concerned with the fabrication methodology of polymeric photonic crystals operating in the visible to near infrared regions and the correlation between the chemical deposition morphologies and the resultant photonic stopband enhancements of photonic crystals.
Multiphoton lithography (MPL) is a powerful approach to the fabrication of polymeric 3D micro- and nano-structures with a typical minimum feature size ~ 200 nm. The completely free-form 3D fabrication capability of MPL is very well suited to the formation of tailored photonic crystals (PCs), including structures containing well defined defects. Such structures are of considerable current interest as micro-optical devices for their filtering, stop-band, dispersion, resonator, or waveguiding properties. More specifically, the stop-band characteristics of polymer PCs can be finely controlled via nanoscale changes in rod spacings and the chemical functionalities at the polymer surface can be readily utilized to impart new optical properties.
Nanoscale features as small as 65 ± 5 nm have been formed reproducibly by using 520 nm femtosecond pulsed excitation of a 4,4'-bis(di-n-butylamino)biphenyl chromophore to initiate crosslinking in a triacrylate blend. Dosimetry studies of the photoinduced polymerization were performed on chromophores with sizable two-photon absorption cross-sections at 520 and 730 nm. These studies show that sub-diffraction limited line widths are obtained in both cases with the lines written at 520 nm being smaller. Three-dimensional multiphoton lithography at 520 nm has been used to fabricate polymeric woodpile photonic crystal structures that show stop bands in the visible to near-infrared spectral region.
85 ± 4 nm features were formed using swollen gel photoresist by 730 nm excitation MPL. An index matching oil was used to induce chemical swelling of gel resists prior to MPL fabrication. When swollen matrices were subjected to multiphoton excitation, a similar excitation volume is achieved as in normal unswollen resins. However, upon deswelling of the photoresist following development a substantial reduction in feature size was obtained. PCs with high structural fidelity across 100 µm × 100 µm × 32 layers exhibited strong reflectivity (>60% compared to a gold mirror) in the near infrared region. The positions of the stop-bands were tuned by varying the swelling time, the exposure power (which modifies the feature sizes), and the layer spacing between rods.
Silver coatings have been applied to PCs with a range of coverage densities and thicknesses using electroless deposition. Sparse coatings resulted in enhanced reflectivity for the stop band located at ~5 µm, suggesting improved interface reflectivity inside the photonic crystal due to the Ag coating. Thick coatings resulted in plasmonic bandgap behavior with broadband reflectivity enhancement and PC lattice related bandedge at 1.75 µm. Conformal titania coatings were grown onto the PCs via a surface sol-gel method. Uniform and smooth titania coatings were achieved, resulting in systematically red-shifted stopbands from their initial positions with increasing thicknesses, corresponding to the increased effective refractive index of the PC. High quality titania shell structures with modest stopbands were obtained after polymer removal.
Gold replica structures were obtained by electroless deposition on the silica cell walls of naturally occurring diatoms and the subsequent silica removal. The micron-scaled periodic hole lattice originated from the diatom resulted in surface plasmon interferences when excited by infrared frequencies. The hole patterns were characterized and compared with hexagonal hole arrays fabricated by focused ion beam etching of similarly gold plated substrate. Modeling of the hole arrays concluded that while diatom replicas lack long-ranged periodicity, the local hole to hole spacings were sufficient to generate enhanced transmission of 13% at 4.2 µm.
The work presented herein is a step towards the development of PCs with new optical and chemical functionalities. The ability to rapidly prototype polymeric PCs of various lattice parameters using MPL combined with facile coating chemistries to create structures with the desired optical properties offers a powerful means to produce tailored high performance photonic crystal devices.
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Ibanescu, Mihai 1977. "Cylindrical photonic crystals." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32306.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (leaves 106-114).
In this thesis, we explore the properties of cylindrical photonic crystal waveguides in which light is confined laterally by the band gap of a cylindrically-layered photonic crystal. We show in particular that axially-uniform photonic band gap waveguides can exhibit novel behavior not encountered in their traditional index-guiding counterparts. Although the effects discussed in each chapter range from hollow-core transmission to zero and negative group velocity propagation and to high-Q cavity confinement, they are all a result of the photonic band gap guiding mechanism. The reflective cladding of the photonic crystal waveguide is unique in that it allows one to confine light in a low index of refraction region, and to work with guided modes whose dispersion relations lie above the light line of air, in a region where the longitudinal wave vector of the guided mode can approach zero. Chapter 2 discusses hollow-core photonic band gap fibers that can transmit light with minimal losses by confining almost all of the electromagnetic energy to a hollow core and preventing it from entering the lossy dielectric cladding. These fibers have many similarities with hollow metallic waveguides, including the fact that they support a non-degenerate low-loss annular-shaped mode. We also account for the main differences between metal waveguides and photonic band gap fibers with a simple model based on a single parameter, the phase shift upon reflection from the photonic crystal cladding. In Chapter 3 we combine the best properties of all-dielectric and metallic waveguides to create an all-dielectric coaxial waveguide that supports a guided mode with properties similar to those of the transverse electromagnetic mode of a coaxial cable.
(cont.) In Chapter 4, we introduce a mode-repulsion mechanism that can lead to anomalous dispersion relations, including extremely flattened dispersion relations, backward waves, and nonzero group velocity at zero longitudinal wave vector. The mechanism can be found in any axially-uniform reflective-cladding waveguide and originates in a mirror symmetry that exists only at zero longitudinal wave vector. In Chapter 5 we combine the anomalous dispersion relations discussed above with tunable waveguides to obtain new approaches for the time reversal (phase conjugation) and the time delay of light pulses. Chapter 6 discusses a new mechanism for small-modal-volume high-Q cavities based on a zero group velocity waveguide mode. In a short piece of a uniform waveguide having a specially designed cross section, light is confined longitudinally by small group velocity propagation and transversely by a reflective cladding. The quality factor Q is greatly enhanced by the small group velocity for a set of cavity lengths that are determined by the dispersion relation of the initial waveguide mode. In Chapter 7, we present a surprising result concerning the strength of band gap confinement in a two-dimensional photonic crystal. We show that a saddle-point van Hove singularity in a band adjacent to a photonic crystal band gap can lead to photonic crystal structures that defy the conventional wisdom according to which the strongest band-gap confinement is found at frequencies near the midgap.
b y Mihai Ibanescu.
Ph.D.
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Fink, Yoel 1966. "Polymeric photonic crystals." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9291.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000."February 2000."
Includes bibliographical references (p. 126-129).
Two novel and practical methods for controlling the propagation of light are presented: First. a design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies is derived and used in fabricating an all dielectric omnidirectional reflector consisting of multilayer films. Because the omnidirectionality criterion is general, it can be used to design omnidirectional reflectors in many frequency ranges of interest. Potential uses depend on the geometry of the system. For example, coating of an enclosure will result in an optical cavity. A hollow tube will produce a low-loss, broadband waveguide, planar film could be used as an efficient radiative heat barrier or collector in thermoelectric devices. A comprehensive framework2 for creating one, two and three dimensional photonic crystals out of self-assembling block copolymers has been formulated. In order to form useful band gaps in the visible regime, periodic dielectric structures made of typical block copolymers need to be modified to obtain appropriate characteristic distances and dielectric constants. Moreover, the absorption and defect concentration must also be ~ontrolled. This affords the opportunity to tap into the large structural repertoire, the flexibility and intrinsic tunability that these self-assembled block copolymer systems offer. A block copolymer was used to achieve a self assembled photonic band gap in the visible regime. By swelling the diblock copolymer with lower molecular weight constituents control over the location of the stop band across the visible regime is achieved, One and three-dimensional crystals have been formed by changing the volume fraction of the swelling media. Methods for incorporating defects of prescribed dimensions into the self-assembled structures have been explored leading to the construction of a self assembled microcavity light-emitting device.
by Yoel Fink.
Ph.D.
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Kurt, Hamza. "Photonic crystals analysis, design and biochemical sensing applications /." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06252006-174301/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.Papapolymerou, John, Committee Member ; Adibi, Ali, Committee Member ; Citrin, David, Committee Chair ; Summers, Christopher, Committee Member ; Voss, Paul, Committee Member.
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Dzibrou, Dzmitry. "Complex Oxide Photonic Crystals." Licentiate thesis, KTH, Microelectronics and Applied Physics, MAP, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11068.
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Microphotonics has been offering a body of ideas to prospective applicationsin optics. Among those, the concept of photonic integrated circuits (PIC’s) has recently spurred a substantial excitement into the scientific community. Relisation of the PIC’s becomes feasible as the size shrinkage of the optical elements is accomplished. The elements based on photonic crystals (PCs) represent promising candidacy for manufacture of PIC’s. This thesis is devoted to tailoring of optical properties and advanced modelling of two types of photonic crystals: (Bi3Fe5O12/Sm3Ga5O12)m and (TiO2/Er2O3)m potentially applicable in the role optical isolators and optical amplifiers, respectively. Deposition conditions of titanium dioxide were first investigated to maximise refractive index and minimise absorption as well as surface roughness of titania films. It was done employing three routines: deposition at elevated substrate temperatures, regular annealing in thermodynamically equilibrium conditions and rapid thermal annealing (RTA). RTA at 500 oC was shown to provide the best optical performance giving a refractive index of 2.53, an absorption coefficient of 404 cm−1 and a root-mean-square surface roughness of 0.6 nm. Advanced modelling of transmittance and Faraday rotation for the PCs (Bi3Fe5O12/Sm3Ga5O12)5 and (TiO2/Er2O3)6 was done using the 4 × 4 matrix formalism of Višňovský. The simulations for the constituent materials in the forms of single films were performed using the Swanepoel and Višňovský formulae. This enabled generation of the dispersion relations for diagonal and off-diagonal elements of the permittivity tensors relating to the materials. These dispersion relations were utilised to produce dispersion relations for complex refractive indices of the materials. Integration of the complex refractive indices into the 4 × 4 matrix formalism allowed computation of transmittance and Faraday rotation of the PCs. The simulation results were found to be in a good agreement with the experimental ones proving such a simulation approach is an excellent means of engineering PCs.
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Zhang, Shuo. "Phosphors and photonic crystals." Thesis, University of Greenwich, 2008. http://gala.gre.ac.uk/8404/.
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Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE phosphors have been prepared using the urea homogeneous precipitation method and firing. Stokes luminescence properties of Y2WO6: RE excited with a FRED (frequency doubled argon ion) UV laser (257 nm) have been studied. The emissions have been assigned to their corresponding energy levels. Differences in the emission spectra of Y2WO6: RE, Y2O2S: RE, Gd2O2S: RE and Y2O3: RE have been attributed to the different site symmetries of the rare earth ions and to the different phonon energies of the lattices. Fine nanostructures present within butterfly wing scales have been faithfully replicated using a precursor Y2O3: Eu phosphor solution. Monodisperse polystyrene spheres and SiO2 spheres were synthesised and they were used to synthesise well ordered bare opal templates. Photonic phosphor crystals of Y2O3: Eu, Tb, Gd and Y2O3: Tm were synthesised using these templates to study the photonic band gap properties. Nano-sized Y2O3: Eu phosphors have been successfully incorporated into mono-dispersed silica spheres which have been assembled into photonic crystals. It has been observed that when light-emitting phosphors (e.g. Y2O3: Eu) and dyes (e.g. acid red dye) are incorporated into the opal structures, their emission spectra are modified when the stopbands of the opals overlap the emission bands of the light-emitting materials.
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Urbas, Augustine M. (Augustine Michael) 1974. "Block copolymer photonic crystals." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29977.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.Includes bibliographical references (p. 151-162).
This thesis explores the photonic properties of block copolymer systems. One dimensionally periodic dielectric stacks are fabricated with symmetric, lamellar forming, copolymer systems: diblock copolymers, solvent swollen BCP materials, and homopolymer swollen BCP blends. Each system exhibits reflectivity in visible spectrum. These materials are also investigated for their phononic band properties by Brillouin scattering. A copolymer forming the three dimensional double gyroid at optically relevant length scales and its reflective properties are presented as well. Experimental results document the initial observation of photonic optical properties related to the microstructure of a block copolymer. One dimensionally periodic, lamellar polymer block copolymer systems of poly(styrene-b-isoprene) are used to fabricate multilayered optical structures with a range of lamellar dimensions. The lamellar repeat of the copolymer morphology is shown to be adjustable by blending symmetric amounts of like homopolymers of lower molecular weight with the copolymer. The composition of the blends remains symmetric and the morphology is shown to remain lamellar. An isopleth of composition is examined and photonic crystals containing up to 60 wt % homopolymer exhibit wavelength selective reflectivity from the ordered morphology. The wavelength of reflectivity is correlated with the lamellar repeat spacing and morphology. The optical properties of solvent swollen ultrahigh molecular weight block copolymers are examined. The wavelength selective reflectivity is shown to correlate with the expected behavior of the phase segregated morphology. Deformation sensitive ordered gels are fabricated by using a non-volatile, alkyl phthalate plasticizer. The optical properties are shown to respond to the material strain. A simple demonstration of the visualization of the strain field of a deforming system is presented. In addition these gels are shown to exhibit phononic band gap behavior. The system is studied by Brillouin scattering and resonant phonons arising from the morphology are predicted and observed. Three dimensionally periodic photonic crystals formed of a double gyroid styrene- isoprene diblock copolymer are also documented. The copolymer material is considered as formed and also after a series of processing steps.
(cont.) Etching of the isoprene matrix is demonstrated yielding a free standing air-styrene double gyroid. This material is then used to replicate the matrix geometry in titania by infiltration with a sol-gel precursor and subsequent pyrolysis. The structure of the double gyroid material is examined via x-ray scattering and electron microscopy. The photonic band properties of the double gyroid structure for multiple constituent materials with a broad range of refractive indices are examined. Features in optical measurements resulting from the double gyroid structure are observed consistent with the 250nm cubic lattice parameter. A block copolymer photonic crystal platform is outlined and presented. Acousto-optic, phononic crystal properties are noted in these materials and applications are discussed. Strategies for creating a block copolymer based material with an absolute band gap ...
by Augustine M. Urbas.
Ph.D.
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Witzens, Jeremy Scherer Axel. "Dispersion in photonic crystals /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05242005-094353.
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Neff, Curtis Wayne. "Optical Properties of Superlattice Photonic Crystals." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/14108.
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Photonic band gap materials, commonly referred to as photonic crystals (PCs), have been a topic of great interest for almost two decades due to their promise of unprecedented control over the propagation and generation of light. We report investigations of the optical properties of a new PC structure based upon a triangular lattice in which adjacent [i, j] rows of holes possess different properties, creating a superlattice (SL) periodicity. Symmetry arguments predicted and quot;band folding and quot; and band splitting behaviors, both of which are direct consequences of the new basis that converts the Brillouin zone from hexagonal (six-fold) to rectangular (two-fold). Plane wave expansion and finite-difference time-domain (FDTD) numerical calculations were used to explore the effects of the new structure on the photonic dispersion relationship of the SL PC. Electron beam lithography and inductively coupled plasma dry etching were used to fabricate 1 mm2 PC areas (lattice constant, a =358 nm and 480 nm) with hole radius ratios ranging from 1.0 (triangular) to 0.585 (r2/r1 = 73.26 nm/125.26 nm) on Silicon-on-insulator wafers. The effects of modifying structural parameters (such as hole size, lattice constant, and SL strength) were measured using the coupled resonant band technique, confirming the SL symmetry arguments and corroborating the band structure calculations. Analysis of the dispersion contours of the static SL (SSL) PC predicted both giant refraction (change in beam propagation angle of 110 for an 8 change in incident angle) and superprism behavior (change in beam propagation angle of 108 for a 12% change in normalized frequency) in these structures. Dynamic control of these refraction effects was also investigated by incorporating electro-optic and nonlinear materials into the SSL PC structure. Wave vector analyses on these structures predicted a change in beam propagation angle and gt;96 when the refractive index inside of the holes of the structure changed from n=1.5 to 1.7. Through this investigation, the first successful measurement of the band folding effect in multidimensional PCs as well as the first explicit measurement of the dielectric band of a 2D PC were reported. In addition, the SL PCs impact on new opto-electronic devices was explored.
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Chen, Parry. "Group velocity analysis of metamaterial photonic crystals and multipole simulation of photonic crystal slabs." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10525.
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Group velocity analysis of metamaterial photonic crystals and multipole simulation of photonic crystal slabs Periodicity is a feature of two topical areas of optics, photonic crystals and metamaterials. Photonic crystals scatter passing light coherently, introducing structural dispersion and creating band gaps where light cannot propagate. Metamaterials use resonant structures much smaller than the wavelength to produce negative effective refractive indexes. When metamaterials are constituents of photonic crystals, new phenomena arise. Firstly, new band gaps appear whenever the average refractive index is zero, occurring independently of Bragg reflections. However, only one dimensional examples have been reported, and its existence in higher dimensions is unknown. Secondly, the group velocity of dispersion relations can be infinite and turn negative, which violates conservation theorems obeyed by lossless structures. These open questions are resolved by using multipole methods, a two dimensional method specialized cylindrical inclusions. Analytical dispersion relations are derived for long wavelengths, demonstrating that zero average refractive index is neither necessary nor sufficient to obtain band gaps. Then, an analytical criterion for infinite group velocity points is derived, existing whenever the modal field is balanced between the positive and negative group index constituents of a photonic crystal. To derive this condition, an analytical tool is developed to calculate group velocities from modal field distributions and material parameters in general lossy dispersive periodic media. Finally, the strengths of the multipole method are applied to simulate a widely fabricated photonic crystal structure: the planar dielectric slab periodically perforated with cylindrical holes. Two structural symmetries are exploited, the vertical translational invariance of the slab, and the rotational invariance of the inclusions, to create a rapidly convergent numerical method. Extensions of the method are possible to defect structures and plasmonic extraordinary transmission gratings.
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Zhou, Ying. "CHOLESTERIC LIQUID CRYSTAL PHOTONIC CRYSTAL LASERS AND PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2706.
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This dissertation discusses cholesteric liquid crystals (CLCs) and polymers based photonic devices including one-dimensional (1D) photonic crystal lasers and broadband circular polarizers. CLCs showing unique self-organized chiral structures have been widely used in bistable displays, flexible displays, and reflectors. However, the photonic band gap they exhibit opens a new way for generating laser light at the photonic band edge (PBE) or inside the band gap. When doped with an emissive laser dye, cholesteric liquid crystals provide distributed feedback so that mirrorless lasing is hence possible. Due to the limited surface anchoring, the thickness of gain medium and feedback length is tens of micrometers. Therefore lasing efficiency is quite limited and laser beam is highly divergent. To meet the challenges, we demonstrated several new methods to enhance the laser emission while reducing the beam divergence from a cholesteric liquid crystal laser. Enhanced laser emission is demonstrated by incorporating a single external CLC reflector as a polarization conserved reflector. Because the distributed feedback from the active layer is polarization selective, a CLC reflector preserves the original polarization of the reflected light and a further stimulated amplification ensues. As a result of virtually doubled feedback length, the output is dramatically enhanced in the same circular polarization state. Meanwhile, the laser beam divergence is dramatically reduced due to the increased cavity length from micrometer to millimeter scale. Enhanced laser emission is also demonstrated by the in-cell metallic reflector because the active layer is pumped twice. Unlike a CLC reflector, the output from a mirror-reflected CLC laser is linearly polarized as a result of coherent superposition of two orthogonal circular polarization states. The output linear polarization direction can be well controlled and fine tuned by varying the operating temperature and cell gap. Enhanced laser emission is further demonstrated in a hybrid photonic band edge - Fabry-Perot (FP) type structure by sandwiching the CLC active layer within a circular polarized resonator consisting of two CLC reflectors. The resonator generates multiple FP modes while preserving the PBE mode from the active layer. More importantly this band edge mode can be greatly enhanced by the external resonator under some conditions. Theoretical analysis is conducted based on 4×4 transfer matrix and scattering matrix and the results are consistent with our experimental observations. To make the CLC laser more compact and miniaturized, we have developed a flexible polymer laser using dye-doped cholesteric polymeric films. By stacking the mirror reflecting layer, the active layer and the CLC reflecting layer, enhanced laser emission was observed in opposite-handed circular polarization state, because of the light recycling effect. On the other hand, we use the stacked cholesteric liquid crystal films, or the cholesteric liquid crystals and polymer composite films to demonstrate the single film broadband circular polarizers, which are helpful for converting a randomly polarized light into linear polarization. New fabrication methods are proposed and the circular polarizers cover ~280 nm in the visible spectral range. Both theoretical simulation and experimental results are presented with a good match.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Paturi, Naveen Kumar. "Analysis of photonic crystal defects for biosensing applications." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4861.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains viii, 70 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 55-57).
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Cui, Xudong. "Photonic crystals with metallic inclusions /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16933.
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Maka, Thorsten. "Thin film opal photonic crystals." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974086991.
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Khokar, Ali Zarrar. "Opal based 3D photonic crystals." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438610.
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Atkin, Dale Mark. "Photonic crystals in planar waveguides." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394394/.
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In this thesis the properties of waveguide modes in photonic crystal planar waveguides are considered. These are waveguides that have been etched with multi-dimensional gratings to create new wavelength dispersive and spatially dispersive behaviours. Analytical models have been developed for the modes in one and two-dimensional photonic crystal waveguides. These describe many of the rich phenomena that may be observed. Weak two-dimensional photonic crystal planar waveguides have been fabricated and their properties have been measured with a specially developed conical prism coupling technique. This thesis demonstrates the advantages of combining photonic crystals with planar waveguides. While future lithographic systems will have sufficient resolution to incorporate photonic crystal regions in integrated optical devices, it has been shown that the waveguide geometry increases the actual grating period required for optical band gaps and so lessens technological difficulties. It is also shown that there are stationary modes which could act as microresonators and that ranges of modes can be suppressed in multimode waveguides. Prism coupling has demonstrated the strong dispersive and frequency selective behaviour of weak photonic crystal waveguides. The future application of this work to efficient, broadband, nonlinear wavelength conversion is proposed.
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Bermel, Peter (Peter A. ). "Active materials in photonic crystals." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/45420.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (leaves 129-139).
I analyze new phenomena arising from embedding active materials inside of photonic crystal structures. These structures strongly modify the photonic local density of states (LDOS), leading to quantitative and qualitative changes in the behavior of active materials. First, I show that the emission spectrum of point-like sources inside an "omniguide" is strongly modified by features resembling one-dimensional van Hove singularities in the LDOS. The resulting overall enhancement of the LDOS causes radiating dipoles to emit more rapidly than in vacuum (known as the Purcell effect). Second, I study optically pumped lasing in three model systems: a Fabry-Perot cavity, a line of defects in a two-dimensional square lattice of rods, and a cylindrical photonic crystal. It is shown that high conversion efficiency can be achieved for large regions of active material in the cavity, as well as for a single fluorescent atom in a hollow-core cylindrical photonic crystal, suggesting designs for ultra-low-threshold lasers and ultra-sensitive biological sensors. Third, I consider a photonic crystal-based light-trapping scheme, capable of compensating for weak optical absorption of crystalline silicon solar cells in the near infrared. For a 2 pm-thick cell, relative efficiency enhancements as high as 35% are expected. Fourth, I explore a way to achieve full ±900 electronically-controlled beam steering using a linear array of one dimensionally periodic elements containing electro-optic materials. Fifth, I consider switching of a single signal photon by a single gating photon of a different frequency, via a cross-phase modulation generated by electromagnetically-induced transparency atoms embedded in photonic crystals. The exact solution shows that the strong coupling regime is required for lossless two-photon quantum entanglement.
(cont.) Finally, I demonstrate that the Purcell effect can be used to tailor the effective Kerr nonlinear optical susceptibility. Using this effect for frequencies close to an atomic resonance can substantially influence the resultant Kerr nonlinearity for light of all (even highly detuned) frequencies. For example, in realistic physical systems, enhancement of the Kerr coefficient by one to two orders of magnitude could be achieved.
by Peter Bermel.
Ph.D.
20
Brossard, Frederic Serge Francois. "Photonic crystals with elliptic scatterers." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614247.
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Almén, Fredrik. "Band structure computations for dispersive photonic crystals." Thesis, Linköping University, Department of Science and Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9610.
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Photonic crystals are periodic structures that offers the possibility to control the propagation of light.
The revised plane wave method has been implemented in order to compute band structures for photonic crystals. The main advantage of the revised plane wave method is that it can handle lossless dispersive materials. This can not be done with a conventional plane wave method. The computational challenge is comparable to the conventional plane wave method.
Band structures have been calculated for a square lattice of cylinders with different parameters. Both dispersive and non-dispersive materials have been studied as well as the influence of a surface roughness.
A small surface roughness does not affect the band structure, whereas larger inhomogeneities affect the higher bands by lowering their frequencies.
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Wang, Jing. "Fabrication and Characterization of Photonic Crystals, Optical Metamaterials and Plasmonic Devices." Doctoral thesis, KTH, Fotonik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33600.
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Nanophotonics is an emerging research field that deals with interaction between light and matter in a sub-micron length scale. Nanophotonic devices have found an increasing number of applications in many areas including optical communication, microscopy, sensing, and solar energy harvesting especially during the past two decades. Among all nanophotonic devices, three main areas, namely photonic crystals, optical metamaterials and plasmonic devices, gain dominant interest in the photonic society owning to their potential impacts. This thesis studies the fabrication and characterization of three types of novel devices within the above-mentioned areas. They are respectively photonic-crystal (PhC) surface-mode microcavities, optical metamaterial absorbers, and plasmonic couplers. The devices are fabricated with modern lithography-based techniques in a clean room environment. This thesis particularly describes the critical electron-beam lithography step in detail; the relevant obstacles and corresponding solutions are addressed. Device characterizations mainly rely on two techniques: a vertical fiber coupling system and a home-made optical transmissivity/reflectivity setup. The vertical fiber coupling system is used for characterizing on-chip devices intended for photonic integrations, such as PhC surface-mode cavities and plasmonic couplers. The transmissivity/reflectivity setup is used for measuring the absorbance of metamaterial absorbers. This thesis presents mainly three nanophotonic devices, from fabrication to characterization. First, a PhC surface-mode cavity on a SOI structure is demonstrated. Through a side-coupling scheme, a system quality-factor of 6200 and an intrinsic quality-factor of 13400 are achieved. Such a cavity can be used as ultra-compact optical filter, bio-sensor and etc. Second, an ultra-thin, wide-angle metamaterial absorber at optical frequencies is realized. Experimental results show a maximum absorption peak of 88% at the wavelength of ~1.58μm. The ultra-fast photothermal effect possessed by such noble-metal-based nanostructure can potentially be exploited for making better solar cells. Finally, we fabricated an efficient coupler that channels light from a conventional dielectric waveguide to a subwavelength plasmonic waveguides and vice versa. Such couplers can combine low-loss dielectric waveguides and lossy plasmonic components onto one single chip, making best use of the two.QC 20110524
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Chigrin, Dmitry N. "Electromagnetic waves propagation in photonic crystals with incomplete photonic bandgap." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971628017.
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Maksymov, Ivan. "Modelling of photonic components based on ÷(3)nonlinear photonic crystals." Doctoral thesis, Universitat Rovira i Virgili, 2006. http://hdl.handle.net/10803/8474.
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En esta tesis se llevó a cabo un estudio de diversas propiedades de los cristales fotónicos 1D y 2D no lineales de tercer orden y de cómo se pueden aplicar dichas propiedades al desarrollo de dispositivos totalmente ópticos (por ejemplo, limitadores y conmutadores, compuertas lógicas, transistores ópticos, etc.). Se propuso una aproximación numérica para calcular las características básicas de los cristales fotónicos no lineales como, por ejemplo, el diagrama de bandas o la transmisión. La aproximación numérica presentada en la tesis tiene ciertas ventajas útiles para cualquiera que diseñe dispositivos ópticos basados en cristales fotónicos no lineales. El sofware desarrollado a base de esta aproximación numérica ha permitido diseñar y simular numéricamente un conmutador totalmente óptico cuyas prestaciones son superiores a las de dispositivos optoelectrónicos convencionales.This dissertation represents a summary of a study of different properties of 1D and 2D third-order nonlinear photonic crystals. It is shown how these properties can be utilized to develop various all-optical devices (e.g. optical limiters and switches, logical gates, optical transistors, etc.) In the dissertation, a novel numerical approximation has been proposed for analyzing the basic characteristics of the nonlinear photonic crystals like dispersion characteristics or transmittance curves. This numerical approximation possesses some important advantages useful in designing all-optical devices based on nonlinear photonic crystals. The software based on its algorithm has allowed to design and simulate a high-production all-optical switching device.
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Trull, Silvestre José Francisco. "Second Harmonic Generation in Photonic Crystals." Doctoral thesis, Universitat Politècnica de Catalunya, 1999. http://hdl.handle.net/10803/6618.
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Photonic crystals emerged at the end of the last decade as a new frame to control the interaction between radiation and matter. The potential advances that such structures could report in photonics technology has lead to an increasing research focused on the implementation of photonic crystals possessing full photonic band gaps, hindering the fact that more simple structures, possessing band gaps in selected directions of space, may also provide strong control of the electromagnetic radiation leading to the observation of many new interesting phenomena. In fact, the scope of this control is not limited to a linear interaction and can be extended to nonlinear interactions of any order. In this work we present a study of the second order nonlinear interaction from nonlinear organic molecules placed within two different types of photonic crystals. First, we will discuss the enhancement and inhibition of the radiation at the second-harmonic frequency of a sheet of dipoles embedded in a 1D photonic crystal. The experimentally observed reflected second-harmonic intensity as a function of the angle of incidence shows sharp resonances corresponding to the excitation of the SH field in a local mode within the forbidden band in the structure, which position depends on the size of the defect, and additional resonance at the high angular band edge, which position is independent of the size of the defect. Comparison among these results and the SH intensity reflected by the same monolayer in free space (which presents a bell shaped radiation pattern as a function of the angle of incidence), shows an enhancement of the radiation at the resonances, and strong inhibition of the radiation at other angles within the gap. Theoretical simulation of the experiment shows a good agreement with the experimental results.
A detailed analysis of the enhancement and inhibition phenomena occurring in these structures shows a clear dependence of the resulting intensity with the position of the monolayer within the defect and with the dipole orientation. The change in phase difference between the oscillating dipoles and the field at the SH frequency at the monolayer as it is moved within the defect is found to play a determining role in the final energy transfer to the second-harmonic field. The resulting enhancement and inhibition of the radiation may be studied in terms of a nonsymmetric contribution of the different components of the field to the energy transfer process.
The second configuration studied in the present work consider the experimental demonstration of second-harmonic generation in a 3-dimensional macroscopically centrosymmetric lattice formed by spherical particles of optical dimensions. In such photonic crystals, the local breaking of the inversion symmetry at the surface of each sphere, allows for the existence of a nonvanishing second order interaction. The growth of the SH radiation is provided by the phase-matching mechanism caused by the bending of the photon dispersion curve near the Bragg reflection bands of this photonic crystal. Experimental evidence of this phase-matching mechanism, inherent of such crystals, is reported in this work. By measuring the SH intensity radiated from several crystals with different concentrations, we obtained the angular dependence of this type of emission and confirmed the surface character of the nonlinear interaction. A simplified theoretical model shows very good agreement with the experimental results. It is important to notice that in this mechanism of SHG, the nonlinearity of the molecule is independent of the phase-matching mechanism, that is inherent to the periodicity of the crystal.
In conclusion, the results obtained show a clear influence of the photonic crystals in the radiated SH intensity, resulting in enhancement and inhibition of the dipoles radiation.
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Euser, Tijmen Godfried. "Ultrafast optical switching of photonic crystals." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57858.
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Woldering, Léon Alexis. "Fabrication of photonic crystals and nanocavities." Enschede : University of Twente [Host], 2008. http://doc.utwente.nl/59403.
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Kucki, Melanie [Verfasser]. "Biological Photonic Crystals: Diatoms / Melanie Kucki." Kassel : Universitätsbibliothek Kassel, 2009. http://d-nb.info/100001326X/34.
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Henning, Andrew John. "Electromagnetic wave chaos in photonic crystals." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/11155/.
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Similarities in the form of the Schrodinger equation that governs the behaviour of electronic wavefunctions, and Maxwell’s equations which govern the behaviour of electromagnetic waves, allow ideas that originated in solid state physics to be easily applied to electromagnetic waves in photonic structures. While electrons moving through a semiconductor experience a periodic variation in charge, in a photonic crystal electromagnetic waves experience a periodic variation in refractive index. This leads to ideas such as bandstructure being applicable to the one and two dimensional photonic crystals used in this work. The following work will contain theoretical and experimental studies of the transmission through, and electric fields within, one dimensional photonic crystals. A slow variation in the structure of these crystals will lead to the bandstructure shifting, with an photonic analogy of electronic Bloch oscillations and Wannier-Stark ladders being seen in these structures. The two dimensional photonic crystals will be shown, through Hamiltonian ray tracing, to support both stable and chaotic ray paths. Examination of the phase space reveals the existence of ‘Dynamical Barriers’, regions in phase space supporting stable ray trajectories that divide separate regions in which the ray trajectories are chaotic. Various manners in which the bandstructure may be varied will be presented, along with a proposed switch that may be made using these structures. While the ray tracing will be carried out in photonic crystals in the limit of infinitesimally thin dielectric sheets, the model will then be developed to show the bandstructure of a photonic crystal made from finite width dielectric sheets, with examples of dispersion surfaces for these structures being presented.
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Fan, Shanhui 1972. "Photonic crystals : theory and device applications." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10344.
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Johnson, Steven G. 1973. "Photonic crystals : from theory to practice." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8644.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001.Includes bibliographical references (p. 147-155).
In this thesis, we explore the design, computation, and analysis of photonic crystals, with a special emphasis on structures and devices that make a connection with practically realizable systems. First, we analyze the properties of photonic-crystal slabs: 2d periodic dielectric structures that have a band gap for propagation in a plane and that use index-guiding to confine light in the third dimension. Such structures are more amenable to fabrication than photonic crystals with full 3d band-gaps, but retain or approximate many of the latter's desirable properties. We show how traditional band-structure analysis can be adapted to slab systems in the context of several representative structures, and describe the unique features that arise in this framework compared to ordinary photonic crystals. We study the possibility of lossless linear waveguides in such systems, and highlight their differences with both conventional waveguides and waveguides in true photonic crystals. Finally, we consider the creation of high-Q cavities in slabs, for which the lack of a complete gap entails unavoidable radiation losses. Two mechanisms for minimizing such losses are described and demonstrated: mode delocalization and the novel far-field multipole cancellation. Next, we present a 3d periodic dielectric structure with a large, complete photonic bandgap. The structure is distinguished by a sequence of planar layers, identical except for a horizontal offset, and repeating every three layers to form an fcc lattice.
(cont.) The high symmetry of the layers means that complex devices could be formed by modifying only a single layer, and their similarity to common 2d photonic crystals allows the direct application of results and experience from those simpler systems. Third, we present and demonstrate general criteria for crossing perpendicular waveguides without crosstalk, based on a priori principles of symmetry and resonance. Finally, we describe a fully-vectorial, 3d algorithm to compute the definite-frequency eigenstates of Maxwell's equations in arbitrary periodic dielectric structures, including systems with anisotropy (birefringence) or magnetic materials, using preconditioned block-iterative eigensolvers in a planewave basis. Many different numerical techniques are compared and characterized. Our implementation is freely available on the Web.
by Steven G. Johnson.
Ph.D.
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Chong, Y. D. (Yi Dong). "Two classes of unconventional photonic crystals." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45169.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 122-126).
This thesis concerns two classes of photonic crystal that differ from the usual solid-state dielectric photonic crystals studied in optical physics. The first class of unconventional photonic crystal consists of atoms bound in an optical lattice. This is a "resonant photonic crystal", in which an underlying optical resonance modifies the usual band physics. I present a three-dimensional quantum mechanical model of exciton polaritons which describes this system. Amongst other things, the model explains the reason for the resonant enhancement of the photonic bandgap, which turns out to be related to the Purcell effect. An extension of this band theoretical approach is then used to study dark-state polaritons in -type atomic media. The second class of unconventional photonic crystal consists of two dimensional photonic crystals that break time-reversal symmetry due to a magneto-optic effect. The band theory for such systems involves topological quantities known as "Chern numbers", which give rise to the phenomenon of disorder-immune one-way edge modes. I describe a system in which time reversal symmetry is broken strongly enough for experimental observation of the one-way edge modes. In addition to numerical studies of this photonic crystal, I develop an analytical effective theory, based on the symmetry of the lattice, that accurately describes its bandstructure.
by Y.D. Chong.
Ph.D.
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Yeng, Yi Xiang. "Photonic crystals for high temperature applications." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92969.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 95-104).
This thesis focuses on the design, optimization, fabrication, and experimental realization of metallic photonic crystals (MPhCs) for high temperature applications, for instance thermophotovoltaic (TPV) energy conversion and selective solar absorption. We begin with the exploration of refractory two-dimensional (2D) MPhC slabs as selective thermal emitters that approach the emittance of a blackbody below a cutoff wavelength, and zero emittance above the cutoff. The theory behind the enhancement of thermal emission is explored, leading to design handles that enable optimization for different applications. The fabrication process and extensive characterization of optimized 2D MPhCs are also presented. Next, we utilize non-linear global optimization tools to further optimize the 2D MPhCs for various TPV energy conversion systems. Performance estimates of realistic TPV systems incorporating experimentally demonstrated spectral control components are also presented. The numerical model is also used to pinpoint deficiencies in current TPV systems to uncover areas of future research to further improve system efficiencies. In particular, we show that air-filled 2D MPhCs suffer from decreased selective emission at larger polar angles, which can be circumvented by filling and coating the 2D MPhCs with a suitable refractory dielectric material. Finally, we explore PhC enhanced silicon (Si) photovoltaic cell based TPV systems numerically. Experiments towards record breaking efficiencies for Si cell based TPV systems are also presented and shown to agree well with numerical estimates, thus paving the way towards widespread adoption of what may be a promising highly efficient, portable, and reliable energy conversion system.
by Yi Xiang Yeng.
Ph. D.
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Shi, Jingxing. "Integrated photonic crystals platform for biosensing." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/423474/.
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Photonic crystals have been shown to be a promising technology for improving the performance of light emitting diodes, solar cells and optical communication components. More recently there has been interest in the application of photonic crystals for bio‐chemical sensing since they provide the potential benefits of high sensitivity, label free, real time detection with low limit of detection. Optical sensing mechanisms such as Surface Plasmon Resonance (SPR), and Evanescent Field (EF) sensing methods are currently popular. These are all sensitive to small changes in refractive index (RI) of part of the device. To date SPR methods provide the highest level of sensitivity but have the disadvantage of requiring an expensive gold coating. AROMA Sensor: As a high sensitivity, low cost alternative to conventional SPR methods, this thesis investigates a new concept for bio‐chemical sensing recently developed at Southampton, which uses vertical projection of leaky transmitted modes of a photonic crystal as the sensing method. We call this Angle Resolved Out‐coupled Mode Analysis (AROMA). This method is highly sensitive to small changes in refractive index at the sidewalls of the holes of a photonic crystal resulting in a strong angular shift of an out coupled beam of light. Changes in RI causes a shift in the projected spot position that can be recorded by a CCD/ CMOS camera. Sensor performance is shown to far exceed normal SPR. Simulation and experimental results demonstrate a sensitivity of 10 degree/RIU from a non‐optimised sensor and simulation results indicate an improved sensitivity of 6500 degree/RIU by optimising the sensor operating point. Responsivity of the sensor was investigated by sequentially depositing a series of sub nm ZnO layers, and was found to be highly linear. Photonic crystal coupler and system integration: Apart from the sensor, a new concept for light coupling is developed and optimised. We extend photonic crystal technology to create a combined light coupler/splitter component allowing arbitrary N‐channel light coupling to a simple slab waveguide device. The coupler is combined with multiple sensors to make a fully functional multi‐channel (4‐12 channels) sensor operating at 785nm. This is integrated into a high refractive index (n=1.7) Silicon Oxynitride (SiON) slab waveguide deposited onto a transparent borosilicate glass substrate. The aim for the slab waveguide was to mimic the refractive index of available polymer materials so that the entire system could eventually be fabricated on a flexible polymer substrate by nanoimprint lithography. Design and modelling: This thesis describes the design and optimisation of each component (sensor, coupler and slab waveguide), presenting in depth background physics and rigorous design methods for each component. 3D models were developed based on Rigorous Coupled Wave Analysis (RCWA) and Finite‐Difference Time‐Domain (FDTD) methods. RCWA models allowed accurate prediction and optimisation of light coupling and projection angles for any selected operating wavelength. FDTD methods allowed careful analysis of the interaction between the light field in the slab waveguide and materials placed in the holes. It also predicts the far‐field projected beam pattern for the sensor. Applications: Capability to detect (dry) monolayer coatings was proven for a simple self‐assembled monolayer molecule coating (p‐tolyltrichlorosilane (TTCS)) and also deoxyribonucleic acid (DNA) was successfully detected, close to physiological levels. To achieve this a complex hybridisation process was developed. Sensor response as a function of self‐assemble molecule (SAM) length and distance from the sidewalls was investigated in detail by using reversible chains of long chain charged molecules (lysine, poly‐lysine, bovine serum albumin protein). A detector surface with a layer of poly‐lysine‐g‐PEG was successfully replaced by a poly‐lysine molecule with larger molecule weight. Sequentially additional bovine serum albumin protein binding with the Polylysine was detected. Capability to detect biomolecules in an aqueous environment is intrinsically difficult for most bio‐sensors. By fabricating the device on a transparent glass substrate, and designing the device to project light backwards through the substrate, it became possible to detect small changes in refractive index for liquids placed on the exposed top surface with no detriment to the readout method. The bulk sensitivity of the sensor for liquids was evaluated by measuring a sequence of glucose solutions with increasing concentrations. A highly linear response was again observed.
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Stumpf, Wolfgang. "High resolution imaging of photonic crystals." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11051695.
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Yu, Xiaofang. "Anomalous spatial dispersion in photonic crystals /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Wu, Yeheng. "Photonic Crystals with Active Organic Materials." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1269618198.
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Thesis(Ph.D.)--Case Western Reserve University, 2010Title from PDF (viewed on 2010-04-12) Department of Physics Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Song, Bong-Shik. "Hetero photonic crystals and their applications." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/145355.
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Lowell, David. "Fabrication and Study of the Optical Properties of 3D Photonic Crystals and 2D Graded Photonic Super-Crystals." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404552/.
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In this dissertation, I am presenting my research on the fabrication and simulation of the optical properties of 3D photonic crystals and 2D graded photonic super-crystals. The 3D photonic crystals were fabricated using holographic lithography with a single, custom-built reflective optical element (ROE) and single exposure from a visible light laser. Fully 3D photonic crystals with 4-fold, 5- fold, and 6-fold symmetries were fabricated using the flexible, 3D printed ROE. In addition, novel 2D graded photonic super-crystals were fabricated using a spatial light modulator (SLM) in a 4f setup for pixel-by-pixel phase engineering. The SLM was used to control the phase and intensity of sets of beams to fabricate the 2D photonic crystals in a single exposure. The 2D photonic crystals integrate super-cell periodicities with 4-fold, 5-fold, and 6-fold symmetries and a graded fill fraction. The simulations of the 2D graded photonic super-crystals show extraordinary properties such as full photonic band gaps and cavity modes with Q-factors of ~106. This research could help in the development of organic light emitting diodes, high-efficiency solar cells, and other devices.
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Hu, Zhen. "Modeling photonic crystal devices by Dirichlet-to-Neumann maps /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ma-b30082559f.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Mathematics in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves [85]-91)
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Shankar, Raji. "Mid-Infrared Photonics in Silicon." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10988.
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The mid-infrared wavelength region (2-20 µm) is of great utility for a number of applications, including chemical bond spectroscopy, trace gas sensing, and medical diagnostics. Despite this wealth of applications, the on-chip mid-IR photonics platform needed to access them is relatively undeveloped. Silicon is an attractive material of choice for the mid-IR, as it exhibits low loss through much of the mid-IR. Using silicon allows us to take advantage of well-developed fabrication techniques and CMOS compatibility, making the realization of on-chip integrated mid-IR devices more realistic. The mid-IR wavelengths also afford the opportunity to exploit Si's high third-order optical nonlinearity for nonlinear frequency generation applications. In this work, we present a Si-based platform for mid-IR photonics, with a special focus on micro-resonators for strong on-chip light confinement in the 4-5 μm range. Additionally, we develop experimental optical characterization techniques to overcome the inherent difficulties of working in this wavelength regime. First, we demonstrate the design, fabrication, and characterization of photonic crystal cavities in a silicon membrane platform, operational at 4.4 μm (Chapter 2). By transferring the technique known as resonant scattering to the mid-IR, we measure quality (Q) factors of up to 13,600 in these photonic crystal cavities. We also develop a technique known as scanning resonant scattering microscopy to image our cavity modes and optimize alignment to our devices. Next, we demonstrate the electro-optic tuning of these mid-IR Si photonic crystal cavities using gated graphene (Chapter 3). We demonstrate a tuning of about 4 nm, and demonstrate the principle of on-chip mid-IR modulation using these devices. We then investigate the phenomenon of optical bistability seen in our photonic crystal cavities (Chapter 4). We discover that our bistability is thermal in origin and use post-processing techniques to mitigate bistability and increase Q-factors. We then demonstrate the design, fabrication, and characterization grating-coupled ring resonators in a silicon-on-sapphire (SOS) platform at 4.4 μm, achieving intrinsic Q-factors as high as 278,000 in these devices (Chapter 5). Finally, we provide a quantitative analysis of the potential of our SOS devices for nonlinear frequency generation and describe ongoing experiments in this regard (Chapter 6).Engineering and Applied Sciences
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Fan, Yun-Hsing. "TUNABLE LIQUID CRYSTAL PHOTONIC DEVICES." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3926.
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Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.Ph.D.
Other
Optics and Photonics
Optics
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Moore, Stephen A. "Photonic crystals as functional mirrors for semiconductor lasers." Thesis, University of St Andrews, 2008. http://hdl.handle.net/10023/557.
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In recent years, interest has grown in the research fields of semiconductor lasers and photonic crystals. This thesis looks at integrating photonic crystals into existing semiconductor laser technology to act as functional laser mirrors. The majority of the research is conducted on a quantum-dot material system. The surface recombination velocity of a GaAs based quantum-dot material is shown to be a similar value to InP material. This allows the creation of fine photonic crystal structures in the laser design without high threshold current penalties. The spectral reflection properties of a one dimensional photonic crystal is studied and found to be an unsuitable candidate for a stand-alone laser mirror, due to its low reflectivity. A two-dimensional photonic crystal W3 defect waveguide is successfully integrated as a quantum-dot laser mirror. Single fundamental mode output is achieved with a typically multi-mode 20 μm wide laser mesa, highlighting the mode selective property of the mirror. A similar two-dimensional mirror is studied for its potential as a dispersion compensating mirror for mode-locked lasers. Initial theoretical analysis shows pulse compression for a suitably designed mirror. Experimental continuous- wave results for the same mirror structure demonstrate the tuning of mirror reflectivity with photonic crystal hole radius. A hybrid silicon-organic photonic crystal laser is demonstrated with output in the visible spectrum. This design is a new type of silicon emitter.
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Ho, Chih-Hua. "Liquid crystals in woodpile photonic crystals : fabrication, numerical calculation and measurement." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404819.
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Both experimental and numerical studies on Liquid Crystal (LC) infiltrated woodpile Photonic Crystal (PhC) are implemented in this thesis.
The most well-known optical phenomenon of PhC is photonic bandgap (PBG). It is observed either in frequency or in spatial domain. The former means for a chromatic plane wave propagating though PhC that a range of frequencies do not transmit but reflect. The later means for a monochromatic focused beam passing though PhC that certain angular components do not transmit but deflect or reflect.
The most well-investigated optical phenomenon of LC is birefringence. It is due to the strong dielectric anisotropy LC possesses. When the applied stimulations (e.g. electric/ optical field or external heater) are present, the orientation of LC molecules and different refractive indices (e.g. polarization or temperature dependent) are observed. The presence of LC inside PhC not only reduces index contrast (where angular BG appears) but also brings the tunability to such LC-PhC composite device. Therefore band-stop angular filter and sensitive refractometer for liquid material are potential applications controlled by multiple external stimulations.
In this thesis, the related physical properties of PhCs and LCs are introduced beforehand. The fabrication of woodpile PhC is also demonstrated. Direct Laser Writing lithography technique is adopted to build microstructures with high resolution up to hundreds of nanometers. A tunable band-stop filter controlled by polarization and temperature is investigated in linear regime. To bridge our investigation to nonlinear regime, dye-doped LC is used to create graded indices inside LC medium corresponding to intensity. Numerical calculations are conducted to the experimental observations.
To sum up, LC-PhC composite device possesses very promising features as demonstrated which could be applied into tunable elements in integrated optical systems and its abundant nonlinear properties remains to be explored carefully.Ambos estudios experimentales y numéricos en cristal líquido (LC) pila de leña infiltrado de cristal fotónico (PhC) se implementan en esta tesis.El fenómeno óptico más conocido de la PhC es la banda prohibida fotónica (PBG). Se observa ya sea en la frecuencia o en el dominio espacial. Los antiguos medios para una onda que se propaga plano cromática aunque PhC que un rango de frecuencias no transmiten sino que reflejan. El medio más tarde para un paso haz enfocado monocromática aunque PhC que ciertos componentes angulares no transmiten, pero desvían o reflejan.El fenómeno óptico más bien investigado de LC es la birrefringencia. Es debido a la anisotropía dieléctrica fuerte LC posee. Cuando los estímulos aplicados (por ejemplo campo óptico / eléctrico o calentador externo) están presentes, se observa la orientación de las moléculas de cristal líquido y los diferentes índices de refracción (por ejemplo, polarización o dependientes de la temperatura). La presencia de LC en el interior PhC no sólo reduce el contraste de índice (donde aparece angular BG), pero también trae consigo la capacidad de ajuste a dicho dispositivo compuesto LC-PhC. Por lo tanto banda eliminada del filtro angular y refractómetro sensible para material líquido son posibles aplicaciones controladas por múltiples estímulos externos. En esta tesis, las propiedades físicas relacionadas de PhC y las LC se introducen de antemano. La fabricación de pila de leña PhC se demuestra. Escritura técnica de litografía láser directa se adopta para construir microestructuras con alta resolución de hasta cientos de nanómetros. Un filtro elimina banda sintonizable controlado por la polarización y la temperatura se investiga en régimen lineal. Para salvar nuestra investigación con el régimen no lineal, LC tinte dopado se utiliza para crear índices graduadas dentro de medio LC correspondiente a la intensidad. cálculos numéricos se llevan a cabo con las observaciones experimentales.Para resumir, dispositivo compuesto LC en la PhC posee características muy prometedoras como se ha demostrado que se pueden aplicar en elementos sintonizables en sistemas ópticos integrados y sus propiedades no lineales abundantes que queda por explorar con cuidado.
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Denisov, Alexey. "Reconfigurable photonic crystals : external field structuring of liquid crystals - polymer composites." Télécom Bretagne, 2009. http://www.theses.fr/2009TELB0104.
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Cette thèse concerne l'étude des composites cristaux liquides (CL) / polymère. Notre but est de concevoir et de fabriquer des cristaux photoniques dont la structure soit reconfigurable par l'action d'un champ appliqué, électrique ou lumineux. Notre première réalisation se base sur l'utilisation de cristaux liquides cholestériques (CLC) stabilisés par un polymère. Les CLC présentent naturellement une structure hélicoïdale périodique, et sont donc des cristaux photoniques à une dimension pour certaines longueurs d'ondes. Pour former un cristal photonique bidimensionnel, nous avons induit une modulation périodique de la structure CLC dans une seconde direction en appliquant un champ électrique. Cette structure a permis de montrer expérimentalement un effet de bord de bande et la possibilité d'ajuster la résonance en modifiant le champ appliqué. Notre deuxième approche se base sur l'effet photoréfractif dans les composites cristaux liquides / polymères dopés par des fullerènes. Dans ces matériaux, nous avons photo-inscrit des réseaux unidimensionnels reconfigurables. Pour améliorer l'efficacité et la résolution, nous avons étudié l'influence de la concentration du dopant, utilisant le fullerène C70 ou le dérivé PCBM-60. Nous avons observé une amélioration de la résolution due à l'effet conjoint d'une augmentation de la concentration en dopant et du mécanisme de piégeage des charges dans le réseau polymère. Nous présentons également une nouvelle façon expérimentale d'exploiter l'effet photoréfractif dans des composites cristaux liquides / polymère, permettant d'améliorer l'efficacité de diffraction, pour mieux satisfaire à des besoins d'applications pratiques.
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Liles, Alexandros Athanasios. "Hybrid photonic crystal cavity based lasers." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12081.
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In recent years, Silicon Photonics has emerged as a promising technology for cost-effective fabrication of photonic components and integrated circuits, the application of which is recently expanding in technological fields beyond tele- and data-communications, such as sensing and biophotonics. Compact, energy-efficient laser sources with precise wavelength control are crucial for the aforementioned applications. However, practical, efficient, electrically-pumped lasers on Silicon or other group IV elements are still absent, owing to the indirect bandgap of those materials. Consequently, the integration of III-V compounds on Silicon currently appears to be the most viable route to the realization of such lasers. In this thesis, I present and explore the potential of an External Cavity (EC) hybrid III-V/Silicon laser design, comprising a III-V-based Reflective Semiconductor Optical Amplifier (RSOA) and a Silicon reflector chip, based on a two-dimensional Photonic Crystal (PhC) cavity vertically coupled to a low-refractive-index dielectric waveguide. The vertically coupled system functions as a wavelength-selective reflector, determining the lasing wavelength. Based on this architecture mW-level continuous-wave (CW) lasing at room temperature was shown both in a fiber-based long cavity scheme and die-based short cavity scheme, with SMSR of > 25 dB and > 40 dB, respectively. Furthermore, by electrically modulating the refractive index of the PhC cavity in the reflector chip, tuning of the emitted wavelength was achieved in the die-based short cavity EC laser configuration. In this way, I demonstrated the suitability of the examined EC configuration for direct frequency modulation. The proposed scheme eliminates the need for wavelength matching between the laser source and a resonant modulator, and reveals the potential of employing low-power-consumption resonant modulation in practical Silicon Photonics applications.
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Mutter, Lukas. "Nonlinear optical organic crystals for photonic applications." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17482.
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Hernández, García David. "Selective thermal emitters based on photonic crystals." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284201.
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Un dels límits fonamentals que afecta l'eficiència de conversió en cèl·lules fotovoltaiques és la distribució espectral de la radiació solar. D'una banda, només els fotons amb energia superior al gap del semiconductor poden convertir-se en electricitat a la cèl·lula. Els fotons de baixa energia no generen parells electró-forat. D'altra banda, l'excés d'energia dels portadors generats per fotons de molt alta energia es perd ràpidament per termalització en el propi dispositiu. Aquests fotons d'alta energia no generen una major energia elèctrica, pel que l'excés d'energia òptica es perd. Per superar aquesta limitació, la investigació s'ha centrat majoritàriament en millorar la conversió directa de fotons d'alta i baixa energia a través de, per exemple, l'ús d'up- i down-converters. Una alternativa menys estudiada consisteix en adaptar la radiació solar al dispositiu com a pas previ a la conversió. Aquesta adaptació es realitza mitjançant l'ús d'emissors selectius òpticament adaptats al semiconductor. Un emissor selectiu és un material amb una emissió tèrmica que ocupa una banda espectral estreta, en comptes d'emetre en tot l'espectre freqüencial. Aquests emissors són una alternativa eficient per obtenir grans conversions, treballant a temperatures al voltant dels 1500 K, donat que un material calentat pel Sol, o una altra font d'energia, pot reemetre llum amb una distribució espectral molt més adequada al dispositiu fotovoltaic. Aquest mode d'operació es coneix com a conversió d'energia termofotovoltaica. A la natura existeixen materials capaços de comportar-se com emissors selectius. Els òxids de terres rares representen un interesant camp d'investigació. Aquests òxids tenen una emissió tèrmica molt baixa en tot l'espectre excepte a certes freqüències. Aquestes freqüències d'emissió són úniques i selectives i provenen de ressonàncies a l'estructura cristal·lina del material. El desavantatge en la seva utilització radica en què la posició espectral d'aquests pico d'emissió, propis del material i la seva estructura, no pot ser controlada. A més, aquestes bandes d'emissió són relativament estretes, generant una baixa densitat de potència radiada. Per tant, existeix la necessitat de treballar amb materials amb una banda d'emissió selectiva que pugui ser dissenyada i controlada convenientment. La solució és l'ús de cristalls fotònics (materials artificials amb propietats òptiques que no existeixen en la natura). Encara que la seva fabricació presenta molts reptes, aquests cristalls artificials permeten el control de l'emissió espontània, suprimint-la o potenciant-la a la banda freqüencial d'interès. Existeixen varies interaccions que permeten aquest control: l'efecte de banda prohibida, la interacció per plasmons o fonons, o l'efecte de microcavitat. Tots permeten modificar l'espectre d'emissió tèrmica d'un material. La present tesis doctoral està dedicada a l'estudi de les propietats d'emissió tèrmica, i estabilitat tèrmica, d'emissors selectius basats en cristalls fotònics. S'han analitzat varies estructures: cristalls fotònics basats en silici macroporós, quasi-cristalls fotònics i microcavitats metàl·liques. També, en col·laboració amb altres grups d'investigació, s'han analitzat les propietats tèrmiques de cristalls col·loïdals. En el present treball, es mostra que els cristalls i quasi-cristalls basats en silici macroporós poden inhibir eficientment la radiació tèrmica de manera controlable, sent a més estables a alta temperatura fins 1500 K. Respecte els cristalls metàl·lics, l'estudi realitzat mostra la seva alta selectivitat espectral, encara que aquests emissors han de treballar a temperatures inferiors a 1100 K per garantir la seva estabilitat estructural i òptica.One of the fundamental limits of conversion efficiency in photovoltaic cells is the broadband distribution of solar spectrum. On one hand, only photons with energy higher than the semiconductor's bandgap can be converted in the device, on the other hand, carriers generated by high energy photons rapidly loose their excess of energy by thermalization with the lattice. To overcome this limitation, and span the useful convertible region of solar spectrum, many approaches have focused on improving the direct photon to electron conversion by the development of up- and down-converters. A less studied alternative, however, is the use of spectrally narrow distributed emitters, optically matched with the gap energy of the photovoltaic cell, instead of direct sunlight. Indeed, a material heated by the sun, or another energy source as methane or hydrogen, can re-emit light with suitable spectral distribution and significant higher power density, improving conversion efficiencies in solar cells. This way of operation is known as thermophotovoltaic energy conversion. Several materials have been considered to be used as emitters in thermophotovoltaic systems. Silicon carbide is a common one, thanks to its high stability at temperatures up to >2000 K. However, its broadband spectral emission limits the conversion efficiency in the photovoltaic device and forces to work at elevated temperatures. Selective emitters, which stand for materials whose thermal emission occupies a narrow spectral region, are a promising alternative to reach elevated conversion efficiencies at lower temperatures. Natural selective emitters as rare earths have attracted considerable research interest as they present unique emission peaks with the highest emittance level. This approach, however, presents some drawbacks, the spectral position where strong emission appears is not controllable, and the width of the emission band is relatively narrow, leading to a low power density emitted by the source. An advantageous way to engineer the selective emission of a thermal source and control the spectral position and bandwidth of strong emission, is by making use of photonic crystals (articial materials engineered to show optical properties that may not be found in nature). The spectral control of the spontaneous emission in such materials is a unique feature of photonic crystals, although their fabrication, mainly in three-dimensions, is still challenging. Several interactions between photonic crystals and radiation have been reported: the photonic bandgap effect, surface plasmon polaritons, phonon polaritons, or the microcavity effect, to give some examples. All these approaches allow engineering the thermal emission of materials to match the energy band of the photovoltaic cell and benefit the optical to electrical conversion efficiency, although some limitations arise when utilized in high temperature thermophotovoltaic systems which will be analyzed during the realization of this thesis. This thesis is therefore devoted to the study of the thermal emission properties and thermal stability of photonic crystal based selective emitters. Various structures have been analyzed: macroporous silicon crystals, photonic quasi-crystals and metallic microcavities. A study in self-assembled colloidal crystals was also started and the preliminary results are presented in the appendix of the document. Here, it is demonstrated that macroporous silicon crystals and quasi-crystals can inhibit thermal radiation in a controllable manner with thermal stability up to 1500 K. The great selective emission properties of metallic microcavities is also demonstrated, although the working temperature of such structures is limited below 1100 K to prevent degradation of the metallic layer.
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Fang, Mei. "3D Magnetic Photonic Crystals : Synthesis and Characterization." Licentiate thesis, KTH, Materials Science and Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11983.
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Kontogeorgos, Andreas. "Optomechanical anisotropy in nanoengineered polymer photonic crystals." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245235.
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Symmetry in photonic crystals is reflected in the structure of their photonic bands and symmetry breaking can result in the development of complete photonic band gaps, leading to enhanced optical properties. This can be difficult for self-assembled nanostructures, due to their restriction by fundamental principles to preferential geometries, but can be achieved through the application of external stimuli. In order to explore such an approach, elastomeric, nanoengineered, polymer photonic crystal structures have been fabricated on a large scale, through a method of shear induced self-assembly of 200nm monodisperse, polymer spheres with a core-shell structure. Determination of the assembly geometry through light diffraction experiments reveals a highly symmetric structure of close-packed, core-shell particles, with its orientation governed by the directionality imposed by the fabrication procedure. In these tuneable photonic crystals, application of external strain at directions of different crystallographic symmetry, accompanied by synchronised optomechanical measurements, reveals strong anisotropic optomechanical properties. It is shown that mechanical properties are primarily dominated by the viscoelastic nature of the shell material, while the strain-induced symmetry breaking reveals previously forbidden resonant peaks. Experiments involving uniaxial extension at principal and non-principal directions verify the underlying symmetry of the crystal lattice and consistently reproduce the anisotropic optical properties, providing information regarding the dual microstructure that controls the optomechanical response of these systems. Simulations based on a model of close-packed hard spheres predict the appearance of secondary resonances and suggest a structural transition from an fcc to a lower symmetry monoclinic crystal lattice. A more elaborate micromechanical model does not verify this transition but predicts the strain dependence of dominant spectroscopic peaks. Experiments involving different crosslinking densities reveal individual contributions from the elements comprising the material's dual microstructure. The inherently low refractive index contrast featured by these polymeric systems forbids the development of full photonic band gaps but symmetry based principles can be applicable to other structures with similar topological restrictions. Results provide a possible route for fabrication of active deformable nanostructures and aid our understanding of self-assembly in these complex systems, leading to optimised large-scale fabrication.